The production of hydrocarbons from subterranean formations is often effected by the presence of clays and other fines which can migrate and plug off or restrict the flow of the hydrocarbon product. The migration of fines in a subterranean formation is often the result of clay swelling, salt dissolution, and/or the disturbance of fines by the introduction of fluids that are foreign to the formation. Typically, such foreign fluids (e.g. drilling fluid, fracturing fluid or stabilizing fluid) are introduced into the formation for the purpose of completing and/or treating the formation to stimulate production of hydrocarbons by, for example, drilling, fracturing, acidizing, or stabilizing the well.
Attempts to diminish the damaging effects caused by introduction of the foreign fluid and the swelling and migration of the components of the formations has included the addition of one or more various shale hydration inhibitors and/or stabilizing agents into such foreign fluids. These work on the principle of the substitution of a cationic species in the clay lattice for a sodium ion. The cationic species is generally selected such that its radius of hydration is less than that of the sodium ion. It is believed that the molecules of the shale hydration inhibitors and stabilizing agents compete with molecules of water for reactive sites. Thus, the possibility of swelling and migration is minimized upon their contact with the formation. As a result, the probability of disintegration of formation is diminished and swelling is inhibited.
Potassium chloride has been widely used as a shale inhibitor/clay stabilizer. In stimulation methods, potassium chloride has often been used as a preflush and/or added to aqueous stimulation methods in order to convert the clay to a less swellable form. While such salts diminish the reduction of formation permeability, they are often detrimental to the performance of other constituents of the foreign fluid. For example, high concentration of such salts is typically required for stabilization of clay (typically 6%). Such salts further produce high chloride levels which are environmentally unacceptable. Other known shale hydration inhibitors/clay stabilizing agents, which have been used include, for example:
WO 98/55733, which discloses the use of at least one organic amine selected from a primary diamine with a chain length of less than 8 carbon atoms and a primary alkyl amine with a chain length of less than 4 carbon atoms:
WO 05/058986, which teaches the use of an amine salt of an imide of a maleic anhydride polymer;
WO 06/013595, which discloses adducts of carboxymethyl cellulose and an organic amine as solid shale inhibitors;
WO 06/013597, which teaches the use of 0.2-5% by wt. of 1,2-diaminocyclohexane to inhibit the swelling of clay;
WO 06/136031, which teaches the use of amine salts having different molecular weights so as to be able to transport into micropore, mesospore and macrospores in the formation and effect cationic exchange therein;
WO 10/040223, which discloses the use of bis-surfactant diamine compounds to reduce clay swelling while drilling is carried out;
U.S. Pat. No. 4,719,021, which teaches incorporating a polyvalent metal/guanidine complex into a drilling fluid to stabilize colloidal clay;
U.S. Pat. No. 4,988,450, which discloses polymers of vinyl acetate combined with potassium salts as an additive for aqueous mud for improving wellbore stability;
U.S. Pat. No. 6,706,667, which discloses a shale-stabilizing additive for water-based drilling fluids including a polymer based on an olefinically unsaturated hydrocarbon with alkylene oxide based side chains;
U.S. Pat. Nos. 6,831,043 and 6,857,485, which teach the use of polyether amines as shale hydration inhibition agents;
U.S. Pat. No. 7,192,907, which discloses quaternary compounds as shale encapsulating agents to at least partially inhibit swelling and aid in the action of conventional shale inhibitors;
U.S. Pat. No. 7,514,392, which teaches the use of bis-cyclohexylamine derivatives as shale hydration inhibitors;
U.S. Pat. No. 7,939,473, which discloses monoquaternary hydroxyalkylalkylamines or poly(trihydroxyalklyalkylquaternary amines) as additives for reducing the swelling of clay in wells;
U.S. Pat. No. 8,026,198, which teaches the use of propylamine derivatives, hydrogenated poly (propyleneimine) dendrimers and polyamine twin dendrimers as shale hydration inhibitors;
U.S. Pat. No. 8,220,565, which teaches the use of a guanidyl copolymer to stabilize a subterranean formation; and
U.S. Pat. No. 8,252,728, which discloses polymers containing hydroxylated structural units which are useful for inhibiting swelling of clays.
There is a continuing need for the development of shale hydration inhibitors/clay stabilizing agents which are substantially odor free, pose little threat to the environment by eliminating substantially all chlorides, and are as at least as effective as the most effective prior art hydration inhibitor/stabilizing agents.